Produced in 2013, the affected batches are due to expire between May and August 2016.

We recommend anyone taking St John’s Wort tablets, or who may have them in their medicine cabinet, to check the batch number against those being recalled

MHRA

PAs are not found in St John’s Wort itself. The contamination is likely to be from accidental collection of local weeds during harvesting, the MHRA said.

Studies in animals have shown some cancers are more common in animals exposed to PAs.

Gerald Heddell, director of inspection, enforcement and standards division at MHRA, said: “We recommend anyone taking St John’s Wort tablets, or who may have them in their medicine cabinet, to check the batch number against those being recalled.

“PAs are known to cause liver problems in humans. Symptoms of liver disorders include yellowing of the whites of the eyes and/or skin, nausea, vomiting, dark urine, abdominal pain and unusual tiredness. If you are experiencing any of these symptoms you should tell your doctor straight away.”

People should return any packs to The Herbal Research Company Ltd c/o QP-Services UK Ltd, 46 High Street, Yatton, BS49 4HJ, UK. Call 01934 838820 or e-mail recall@QP-Services.com to receive a pre-paid stamped addressed envelope.